As reaction vessels of this type, there have been suggested ones involving means or structures for controlling the rise of a gas temperature resulting from an exothermic reaction during operation. FIG. 1 attached hereto exemplarily shows the effect of a temperature on a methanol equilibrium concentration in a methanol synthesis reaction, and as is definite from it, the methanol equilibrium concentration will be low along with the rise of the temperature, so that an economy of an industrial plant will be impaired. Therefore, the above-mentioned suggested reaction vessels have attempted to eliminate such a disadvantage. FIG. 1 above has been quoted from "Methanol", Nozawa, Vol. 46, No. 9, p. 507 (1982) and calculated values have been obtained by setting, to 4, a ratio of H.sub.2 to CO in the reaction of CO+2H.sub.2 .fwdarw.CH.sub.3 OH. In this reaction, a reaction rate is limited even if a catalyst is employed, but naturally the reaction rate will be low with the fall of the temperature. Therefore, it is industrially preferred that the operation of the reaction vessel is carried out within a certain proper temperature range in view of catalyst performance. In the case of synthesizing methanol from a mixed gas containing hydrogen, carbon monoxide and carbon dioxide as major component materials by the use of a copper catalyst, the inventors of the present application have the understanding that a preferred temperature lies within the range of 220.degree. to 280.degree. C. and a preferred and economical pressure (total pressure) of the gas lies within the range of 50 to 300 kg/cm.sup.2 .cndot.G, but these preferred ranges can vary dependent upon any future improvement in the catalysts used.
A known method for adjusting this temperature is disclosed in, for example, Japanese Patent Publication No. 38568/1982.
This known technique, as shown in FIG. 2, comprises causing a pressurized mixed gas, i.e., an unreacted gas A consisting of hydrogen, carbon monoxide, carbon dioxide and the like which has previously been heated to a suitable temperature, to flow through a catalyst filling reaction pipe 2 in a reaction vessel 1 upward from a lower position thereof in order to accomplish a methanol synthesis reaction, and getting rid of the resultant reaction heat via the latent evaporation latent heat of water, having a suitable pressure and a saturated temperature, which is brought into contact with the outer surface of the reaction pipe, whereby a temperature of the mixed gas in the reaction pipe is maintained in a suitable condition range. In FIG. 2, reference symbol B represents a reaction gas, and numerals 3 and 4 are water to be supplied and water vapor to be discharged, respectively. Practically, a number of reaction pipes can be disposed therein, but in FIG. 2, simplification is made for clarity.
In the case of the above known example, however, it is necessary to previously heat, by a heat exchanger, the feed gas which will be forwarded to the reaction vessel, which fact means that it is poor in economy. Further, as is definite from FIG. 3 which is a sectional view of the reaction pipe 2 in FIG. 2, the pipe 2 is packed with a grainy catalyst 4 in the form of a column, therefore the central portion of the catalyst layer 4 is so considerably away from the heat transmitting surface that a sufficient cooling (control of a reaction temperature of the gas, i.e, maintenance of an optimum temperature) is disadvantageously difficult to achieve.
The present inventors have already suggested a double pipe type exothermic reaction vessel by which the above-mentioned drawbacks are eliminated (Japanese Patent Application No 213724/1983), but the present invention intends to provide a further improved reaction vessel.